Tree Style tabs problems may be addon conflict Rated 5 out of 5 stars
Some problems people are seeing may be a conflict with the "Collusion" add-on.
Tree Style Tabs is essential to me. So, when I started seeing the "stacking new tabs unusably on top of others" behavior, I wasn't happy. But, since it started happening right after I installed Collusion, I tried disabling that plugin. When I did, the problem got a little better. I completely un-installed it, and that didn't help, but when I re-installed Tree Style Tabs, it looks like everything is back to normal.
I wish I could use Collusion, but it's a "fun for a bit" sort of thing, whereas Tree Style Tabs is vital, need it every day functionality.
(Note: This is on Linux.)